Stress And Fatigue Analysis Of Recirculating Ball Power Steering Gear

With the rapid development of China’s automobile industry, the steering gear technology has been improved in recent years. As one of the key assemblies of automobile, steering has a great influence on the car’s operating performance. Recirculating-ball power steering gear is widely used on many trucks and SUVs for the advantages of convenient operation and high transmission efficiency. The abrasion performance and fatigue performance is particularly important. However, a lot of traffic accidents have occurred because of the damage of thecar steering system, such as screw fracture and Recirculating ball broken.So, More attention has been paid on steering gear’s reliability with the main characteristics ofabrasion performance and fatigue performance.Recirculating-ball steering gear has two level transmission vice:steering screw nut pairandrack sector gear pair. Recently, most of the research onrecirculating-ball steering gear are based on the method of rigid body dynamics and static linear finite element method. Those studies have some shortages, they have not taken consider of the dynamic working process of the steering gear and the coupling process of the two levels of transmission. While the explicit dynamic finite element method can analysis the dynamic working process of the recirculating-ball steering. However, the recirculating-ball steering has a complex structure and a long time working process, which belong to a nonlinear problem of large displacement, large rotation and multiple contacts. Besides, some components of the recirculating-ball steering have a great difference in size(steel ball diameter is 8mm, shell length is 280mm), so the FE model have millions of elements and little time step. As a result, researchesby explicit dynamic finite element method on recirculating-ball steering have not reported.This paper has established a finite element model of the recirculating-ball steering, including two-stage transmission vice, shell and steering arm, which can reflect the real working condition of the steering.The connection and contacts of the components was considered, and the hydraulic system was considered by the way of equivalent pressure. The working process of the recirculating-ball steering is analysed by explicit finite element software LS-DYNA, stress,strain,displacement of the main components(recirculating ball, worm gear, ball nut rack, sector gear) was gained. Finally, Import the FE result to nCodeDesignLife to calculate the fatigue life of the main components.